1. Field of the Invention
The present invention relates to a swing-arm-type suspension device for a vehicle.
2. Description of Background Art
A swing-arm-type suspension device for a vehicle is known in the background art. Specifically, one end of a swing arm is mounted on a vehicle-body-side pivot shaft. A rear wheel is supported on another end of the swing arm. An upper end of a cushion unit (shock absorber) is mounted on the swing arm. Furthermore, a lower end of the cushion unit is connected to the vehicle-body side and the swing-arm side by way of a link mechanism (see, for example, Japanese Patent Application Laid-Open No. 2002-68066).
In FIGS. 1 and 2 of the above document, a swing-arm-type suspension device 30 having the following structure is described. Specifically, a pivot shaft 31 is mounted on a rear portion of a power unit 16. A front end of a swing arm 32 is swingably mounted on the pivot shaft 31. A rear wheel 33 is mounted on a rear end of the swing arm 32. An upper end mounting portion 46, which is mounted on an end portion of a cushion unit 34 is swingably mounted on an upper bracket 36 of the swing arm 32. A lower end mounting portion 43, which is mounted on an end portion of the cushion unit 34 and a lower portion bracket 38 of the swing arm 32 are connected to a link mechanism 37. Furthermore, the link mechanism 37 is connected to a rear lower portion of the power unit 16.
When a vehicle body starts rolling during cornering or the like, the rolling of the power unit 16 on the vehicle body side is transmitted to the swing arm 32 by way of the pivotal shaft 31. The rolling motion is then transmitted to the rear wheel 33 from the swing arm 32. However, the rolling of the vehicle body is transmitted to the rear wheel 33 with a delay following the rolling of the power unit 16. Depending on the rider, there exists a demand for a swing-arm-type suspension device for a rear wheel that can transmit the rolling of the vehicle body to the rear wheel 33 substantially with no delay.